Abstract

Host preferences of the aphelinid parasitoid, Aphelinus sp. nr. varipes, on the wheat aphids Diuraphis noxia (Kurdjumov), Schizaphis graminum (Rondani), Rhopalosiphum padi (Linnaeus), Sitobion avenae (Fabricius) and Metopolophium dirhodum (Walker) were tested in the laboratory. This parasitoid was introduced from the Ukraine where it was collected from D. noxia. An instar preference test was also conducted with D. noxia as host aphid. Preference for oviposition on a particular instar of the aphid could not be demonstrated. Before preference tests were conducted, the Aphelinus sp. was preconditioned on each aphid species. The parasitoid failed to complete its development on R. padi and S. avenue. During the preference test, however, parasitoid females did oviposit in each of the five wheat aphid species. Regardless of the aphid species on which the parasitoid was reared, significantly more eggs were laid in D. noxia, showing a significant preference for oviposition on this species. No clear preference was found for feeding on a specific aphid species.